In certain phases of diagnostic research, a pure culture of bacteria is introduced by means of a needle into various media contained in tubes. According to present practice, a tube is held in one hand while removing the screw top with the other. Then, a needle with the bacteria on it is grasped and introduced into the tube. After the needle is withdrawn, the screw top is replaced loosely to allow venting of the gases which are generated by the bacterial action on the media inside the tube. Then the tube is racked and the process of grasping a tube, removing the top, introducing the bacteria and replacing the top, remembering to allow for venting, is repeated for each of the two or more media into which the bacteria is to be introduced.